I just purchased a TR-4 at a hamfest. I have worked on several before , but this one is different. It has a noise blanker (an add-on kit) installed and the schematic is closer to a TR-4c than a plain TR-4. The noise blanker is switched by an add-on switch behind the Tune control. The only difference from a TR-4c that I can see is that the crystal calibrator is a 6BA6 ( it's a 6BZ6 in a TR-4c), and it does not have the noise blanker switch on the lower right corner of the front panel. It has two 8 pole filters, not a soup can. Is there a schematic and manual for this particular radio, or can I use the TR-4c manual to work on it? Is this a late-model TR-4 before the c came out? Thanks KD8CN
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